- Open the file you want to modify in Photoshop
- Create a duplicate layer of the image
- In the layer palette click on the drop down menu
- Select "Duplicate Layer"
- It will ask you to name the new layer then click "OK"
- Make sure that the layer you just created is selected in the layers palette
- Go to Image>Adjustments>Desaturate
- Go to Layer>Layer Mask>Reveal All
- A new white box will appear next to the thumbnail of the layer with a chain link between the two boxes. Make sure that this box is selected
- Making sure the the foreground color is black, begin painting with the brush tool
- Zoom in and out as needed and don't forget to adjust the brush size (in the property bar at the top) to get all the smaller places